Traditionally, pharmaceutical and therapeutic actives can be administered to the body by a number of routes including ingestion, injection, inhalation, and topical application. Absorption of an active by ingestion, injection, and inhalation generally gives systemic distribution of the active throughout the body. This systemic distribution of the active may be undesirable for three reasons. First, these modes of administration are non-specific. The active is distributed through the entire body and not localized. Secondly, there may be undesirable effects such as toxic or irritating reactions on nontarget organs or regions. Finally, to achieve the desired effect at the target organ or region, a higher dosage than might otherwise be desired must be administered to compensate for systemic dilution of the active.
Because of these deficiencies, topical application of actives is a highly desirable alternative: the dosage is reduced and the active is confined to the region of the body where it is applied. Thus, systemic distribution of the active throughout the body is obviated. In contrast to systemic delivery, topical delivery refers to the application of an active in a manner so that it acts primarily at the site of application. Typical sites of topical delivery include application to the dermal, opththalmic, and mucous membranes and tissues such as the skin, eyes, ears, mouth, nose, throat, rectum, vagina and urethra.
However, despite these advantages of topical delivery, most current topical delivery formulations are not very efficient and are therefore of limited utility. There are four reasons for this inefficiency of current topical delivery technology. First, skin and mucous membranes possess good barrier properties and the permeability of most actives through these is generally poor. Second, actives applied topically are subject to migration and loss due to perspiration, natural tissue lavation and mechanical action. Third, because most pharmaceutical or therapeutic actives are relatively simple, low molecular weight compounds or mixtures, these actives are not applied alone, but in combination with a variety of additives to deliver the active to the application site and control the dosage. Fourth, the choice of a proper delivery system can minimize undesirable crystallization of the active, and hence optimize its availability in its active form. Most current topical delivery systems are petrolatum based cremes and ointments. These unctuous formulations are undesirable because they are at best uncomfortable and messy when applied, and at worst, irritating and potentially damaging to skin and mucous membranes (mucosa).
Accordingly, one or more of the following objects will be achieved by the practice of the present invention. It is an object of this invention to provide delivery systems containing pharmaceutical and therapeutic actives which can be administered to a desired topical or mucous membrane site of a subject, including human beings. Another object of this invention is to provide delivery systems comprised of certain aminopolysaccharides which may contain pharmaceutical and therapeutic actives. A further object of the invention is to provide delivery systems which avoid many of the undesirable features of ointments and salves and yet maintain and transmit the necessary amount of active ingredient to an appropriate site of the body. Another object of this invention is to provide processes for the preparation and use of the systems containing chitosan derivatives and the active component. These and other objects will readily become apparent to those skilled in the art in light of the teachings herein set forth.